International AHC Day Date in the current year: January 18, 2025

Hemiplegia is the loss of motor control (paralysis) on one side of the body, which can be caused by a variety of medical problems. The most common cause of hemiplegia is stroke, but it can also be caused by traumatic brain injury, tumors, trauma, and certain congenital conditions.

Patients with alternating hemiplegia of childhood (AHC) experience transient episodes of hemiplegia, often referred to as attacks. They can vary in severity from mild weakness (hemiparesis) to complete paralysis and last from minutes to weeks. The onset of these attacks is usually between 6 and 18 months of age, hence the name of the condition.

Hemiplegic attacks are the main symptom of AHC, but they are not the only one. The condition is associated with a wide range of neurological symptoms, which can be divided into two groups: paroxysmal and non-paroxysmal.

Paroxysmal symptoms include various types of involuntary movements, such as spasms, seizures, and nystagmus. Approximately half of patients with AHC also have epilepsy, which often leads to AHC being misdiagnosed as epilepsy. Non-paroxysmal symptoms may include mental impairment (developmental delay, social problems), usually mild or moderate, and ataxia (lack of voluntary coordination of muscle movements).

AHC is very difficult to diagnose because it is extremely rare and complex. In addition, there is no diagnostic test for AHC, making it a diagnosis of exclusion. AHC is a lifelong condition associated with a generally poor outcome, as there is no cure and no truly effective treatments. In the long term, hemiplegic attacks cause permanent damage to the body.

On January 18, 2012, a group of scientists made a landmark discovery showing that approximately 70-80% of cases of AHC are caused by a mutation in the ATP1A3 gene, which provides instructions for making one part (the alpha-3 subunit) of a protein known as the sodium-potassium pump, which is critical for the nervous system. The anniversary of this discovery has been designated as AHC Awareness Day.

The main goal of International AHC Day is to raise awareness of this rare disease and highlight the importance of further research into AHC. Since about 20% of patients diagnosed with AHC do not have a mutation in the ATP1A3 gene, experts believe that there are other genes associated with AHC that have not yet been discovered, so it is important to continue research.

AHC Awareness Day is supported and promoted by AHC organizations around the world, such as the Spanish Association of Alternating Hemiplegia of Childhood (AESHA), Alternating Hemiplegia of Childhood UK (AHC UK), the IAHCRC International Consortium for the Research on Alternating Hemiplegia of Childhood, and others.